The Tale was preserved among the Wise of the Third House of the Edain, the People of Marach. Adanel was a Wisewoman directly descended from Marach and the sister of Hador; the Tale was especially connected with her because she told it to another Wisewoman of the Edain, Andreth, and from her it was passed down to later generations, until the Númenóreans of a much later time period wrote it down. The Third House was the only group of the Edain who preserved a clear tradition of this story, since the other kindreds of Men tried to forget it.

The Tale of Adanel is "compressed in time-scale", which makes it difficult to ascribe its events to a particular time or place. Most of it seems to cover a period of several years, beginning soon after the Awakening of Men at the first rising of the Sun. It ends with an allusion to the arrival of the Edain at Beleriand, which took place about 300 years after the creation of Mankind.

Though the Tale was preserved by the loyal Edain, it is actually told from the point of view of one of those still loyal to Melkor but oppressed by his higher-ranking servants, as shown from the pronoun usage. The narrator speaks of those who escaped from Melkor's service, as well as those who lead the worship, in the third person.

The story begins with the Voice of Ilúvatar speaking in the hearts of the newly-created race of Men concerning their making and their purpose in the world. Soon after they hear this Voice for the first time, Men begin to explore their surroundings and make words. However, they find this endeavour difficult, and often ask the Voice for help. But the Voice avoids giving them direct answers to their questions, since Ilúvatar prefers that they discover the world themselves "and become wise". Most of the Men thus quit speaking to the Voice.

After some time, a being who looks like them but is "greater and more beautiful" appears among the people, and offers his services as a teacher. This person is actually Melkor in a fair disguise. The race of Men listen to his teachings, since he proves more willing to impart information to them than the Voice. Melkor speaks often of the Darkness and its power, and during an apparent solar eclipse he uses the fear of Darkness to get Men to bow before him and abjure the Voice, since he claims that it is the Voice of the Dark that wishes to devour them. Once he has their loyalty, Melkor orders the people to build a House to his worship, where they pray to him and hear his commands. Every single Man living is said to have bowed there, thus bringing the Shadow upon them all.

The Voice of Ilúvatar speaks one more time, and pronounces judgment upon Men for these deeds. Soon after, the first deaths begin to occur, the Earth and its creatures turn against Mankind, and some of Melkor's most favored servants begin to oppress the others brutally. At this time, many Men begin to hate and fear Melkor, seeing him for what he is. Eventually, a group of them decide to escape and find a place free from Melkor's influence, though they are still under the doom of Ilúvatar. Though many are hunted down by those still loyal to the Dark Lord and burned in his House, some make it to the West of Middle-earth—the ancestors of the Edain.